The present invention pertains to a lift intended to transport persons between a lower level and an upper level, for particular installation in dwellings to facilitate access to floors for users with reduced mobility such as elderly, handicapped persons.
In this area lifts are known comprising a cabin or horizontal platform able to be translated vertically within a vertical shaft from a lower floor to an upper floor, or the reverse, using actuating means; this is the case for example in French patent FR 2 584 694 which describes a hydraulic lift with cabin. The hydraulic lift comprises a cabin which is linked, via support means and return pulleys, to a hydraulic cylinder which can be moved in the direction of travel of the cabin, the cabin being raised and lowered through the inflow and outflow of a working liquid. The inflow of working liquid to the hydraulic cylinder is made by means of a pump driven by a motor. Therefore the piston rod of the hydraulic cylinder anchored fixedly with its upper end, which may emerge under the effect of weightlessness to cause the cabin to rise, is linked at its end to a pulley guiding the support means anchored fixedly at one of their ends and anchored to the cabin at their other end.
Although the actuating means of this type of lift are of limited volume, the installation of this type of lift requires structural work within the dwelling which adds considerably to the installation costs of this type of lift.
So-called hydraulic lifts are also known whose cabin is linked to the piston of a hydraulic cylinder to lower and raise said cabin through the respective inflow and outflow of a working liquid in and out of the hydraulic cylinder; this is the case for example in German patent DE 3 136 739. The hydraulic cylinder is connected via a pump to a pressure accumulator in the form of a cylinder whose piston is loaded by a counterweight through the piston rod.
It will be noted that the length of the hydraulic cylinder corresponds to the maximum travel distance of the cabin, so that the elevation height of the cabin is particularly limited.
To overcome this drawback, hydrostatic driving devices have already been imagined allowing long travel distances. This is the case for example in European patent EP 0 374 500 describing a scissor lift system which can be used in garages in particular to raise vehicles, comprising two pairs of legs mounted scissor fashion, one of the free ends of one leg of a pair pivoting about a fixed pin secured to the floor, the other end pivoting about a pin sliding along one of the side edges of the lift frame, the other leg having one end pivoting about a fixed pin secured to the side of the lift frame and its other end pivoting about a pin sliding along the floor. The two legs of a pair are pivot mounted about a pin supporting a connecting rod pivotally connected to the ends of the two hydraulic rams acting as actuating member about an axis that is off-centred from its assembly axis, able to pivot 90° between a globally horizontal position and a position in which it is locked in rotation. The connecting rod is advantageously provided with rollers to allow rapid rising of the pivot pin linking together the two legs of a pair when the lift frame is in lower position. Also the existence of the connecting rod itself, through its pivoting and by gear reduction, enables rapid rising of the pivot pin linking together the two legs of a pair.
This type of lift has the disadvantage of requiring structural or demolition work at the bottom of the shaft to form a pit located under the lower level to house the hydrostatic driving device, which considerably adds to the installation costs of said lifts. Failing this, the lift platform cannot lie flush with the floor level when the lift is in lower position, the legs and actuating body being arranged underneath the platform.